It is often desirable to treat livestock with drugs to control parasites. Parasiticides (or drenches) are often applied to the skin (as a pour-on liquid) or administered orally. Livestock may also be injected with these drugs. To control parasites, the livestock typically must be rounded up and placed in a holding area and separated by size so that each animal may be properly dosed with the drug. Once treated, the animal is released until the next dosing is required. Preferably a record is made of the drug and dose administered and the date of application.
Unfortunately, the process of separating the animals by size, administering the requisite dose to each size group of animals in turn and keeping manual records, is time consuming and expensive. This tempts the farmer into overdosing an animal to prolong the period during which the drug is present at effective levels. Furthermore, to avoid the sorting by size the farmer may rely upon his judgment to estimate the dosage to administer to each animal.
It should be appreciated that dispensing liquid in a farm environment is quite a different proposition to that in a more controlled situation such in a laboratory or factory.
Firstly, the environment in which the operator works is quite changeable.
For example, the reservoir holding the liquid (hereinafter referred to as drench) may be in a backpack on the operator. In other situations there may be a larger drench container situated on the ground, on a vehicle or elsewhere.
All these different environments can affect the operational dispensing device as the varying volumes, heights (which can affect pressure head) and container shapes and conduits to the dispensing outlet can lead to inconsistencies in the amount being dosed by the operator.
This is obviously an undesirable situation given that relatively precise doses of treatment liquid are required to ensure that the treatment is effective and the animal is either not overdosed or underdosed.
Another situation which is fairly specific to the drenching of animals is that quite often the same dispensing device is used to dispense a variety of treatment liquids, each having different viscosities or flow properties. Thus, it can take longer to dispense a certain volume of liquid having a high viscosity than the equivalent volume of a liquid having a low viscosity. This can be frustrating to the operator of the dispenser as often hundreds of animals are being treated at a time.
Whitford's New Zealand Patent No. 224789 describes a drench apparatus which attempts to overcome some of these difficulties by providing an animal scale with a weight transducer which supplies a signal used to regulate a motorised drench dosage pump to dispense a dose in proportion to the animal's weight.
A disadvantage with this system is the necessity of providing the scale, which is expensive and relatively massive. Not being readily portable it lacks versatility and does not lend itself to use away from the normal holding area on the farm, where it would typically be permanently installed. Moreover, this known system requires manual record keeping and provides no indication of the progress of the dispensing operation, such as the number of animals treated.
Eidson Associates' New Zealand Application No. 332852 also attempts to overcome a number of these problems by providing an automatic drenching system. This overcomes the problem of operator fatigue as an electronic switch on the hand held drench gun activates a peristaltic pump which pumps fluid through to the drench gun. However, this invention does not address a number of the problems in the prior art, including storage of information, changing environmental conditions, fluids of different viscosity and easy recalibration.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.